A conventional liquid crystal display (LCD) requires a backlight module for displaying images, and such backlight module usually includes a light source and a light guide plate for guiding scattering of light emitted from the light source and exiting from the backlight module, so as to improve the luminance and ensuring the uniformity of the luminance of the LCD.
Referring to FIG. 1, a conventional side-emitting backlight module includes a light guide plate 91, a light source 92, and a reflector 93. The light guide plate 91 has a light exit surface 911, a reflection surface 912 opposite to the light exit surface 911, and a light-incident surface 913 that is connected between the light exit surface 911 and the reflection surface 912, and which separately faces the light source 92. Light emitted from the light source 92 will enter the light guide plate 91 through the light-incident surface 913 and mostly exit from the light guide plate 91 through the light exit surface 911. The reflection surface 912 and the light-incident surface 913 are respectively formed with diffusive microstructures (not shown) so as to more evenly distribute the light exiting from the light exit surface 911. The reflector 93 is disposed opposite to the reflection surface 912 and the light exiting from the reflection surface 912 will be reflected back into the light guide plate 91, thereby increasing utilization of the light by the conventional side-emitting backlight module. Additionally, the light source 92 has a light-exiting surface 921 for emission of the light generated by the light source 92 therefrom. The light-exiting surface 921 of the light source 92 corresponds in position and size to the light-incident surface 913 of light guide plate 91 so as to reduce light leakage and light energy loss.
Referring to FIG. 2, the light guide plate 91 of the conventional side-emitting backlight module has a visible area 911a in positional correspondence to a screen of the LCD (not shown). For fulfilling requirements of full screen and narrow bezel for the LCD, a distance (d) between the visible area 911a and the light-incident surface 913 gradually becomes narrower as technology advances. In addition, the diffusive microstructure formed on the light-incident surface 913 tends to be more compact and microminiaturized, and the diffusive microstructure formed on the reflection surface 912 tends to have a relatively high light directivity based on the needs of luminance. These developments of the light guide plate 91 may increase the need for a greater extent of even light distribution in areas near the light-incident surface 913. Existing designs of the light guide plate 91 may unfavorably result in grated speckles in the areas near the light-incident surface 913. When the light exit surface 911 is formed with a V-CUT or R-CUT microstructure, the light exiting therefrom may easily have the form of dipped beams.